I switched to AntennaPod and VLC. I realized I don't need algorithmic recommendations or streaming. I know what I want and my phone has plenty free space.
Also, for anyone who (like me) doesn't regularly keep up with micro-SD prices, you may be happy to find that 128GB cards are now dirt cheap. You don't have to juggle what's on your phone anymore. I don't know when this happened, but that's multiple months' worth of audio with all your internal storage free for pictures or the like.
Unfortunately, sometimes you have. Apps can not moved to SD card depending on Android version or vendor.
Also, I use a Syncthing oneway folder to automatic sync downloaded music to phone.